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Are Borates Safe to Use?

Since I've found different, though similar, sources of information and have been asked about this in multiple posts, I thought I would consolidate some information on the safety of using borates in a pool (or spa).

It started with information in this report where the most reasonable number for the highest No Observed Adverse Effect Level (NOAEL) was 8.8 mg/kg/day (note that borates are meaured in units of Boron so this is milligrams of Boron per kilogram of body weight). The main adverse effect was seen in male dogs (at 29 mg/kg/day) some of whom had smaller testicles at higher borates levels after long-term (daily) exposure to higher borates levels. So to be safe, dogs should be trained not to drink every day from a pool using borates (one liter of 50 ppm Borate water drunk by a 22 pound dog is 5 mg/kg/day).

I then ran into this EPA report (see also this EPA report) that also quotes the 8.8 mg/kg/day as an NOAEL limit, but they use a factor of 100 Margin of Exposure (MOE) to be extra safe for humans (i.e. assuming that humans might be more sensitive than dogs since no direct toxicity tests were done on humans). Pool doses above 360 ppm Borates [EDIT] actually it's 52-53 ppm [END-EDIT] exceeded the margin of exposure limit for 7-10 year old swimmers assuming they accidentally drink 2 ml per day [EDIT] actually 38 ml (around 2-1/2 tablespoons) per day at 52-53 ppm [END-EDIT]. At 50 ppm Borates, [EDIT] an infant [END-EDIT] would have to drink 14 ml (about 1 tablespoon) per day of pool water. With no margin of exposure, this would be around 1.5 quarts per day. [EDIT] This assumes an 8 kg (17.6 pound) infant such as a 6-month old boy or 8-month old girl; a 7-year old weighs more like 23 kg (around 50 pounds) so could tolerate about three times as much, 38 ml per day or around 2-1/2 tablespoons every day and remember that this is with a safety margin of 100; with no margin of exposure it's over a gallon per day. [END-EDIT]

So are borates safe? It's all relative. There was no significant dermal (skin absorption) risk so it really comes down to regular drinking of pool water (one day or two means little; the studies on [EDIT] first noticeable effects [END-EDIT] were long-term daily doses). Even then, the risk is low, but if either a dog or a child were to drink significant quantities of pool water every day, then it would be better to keep them away from the pool water. The Borates do not bio-accumulate; they are naturally found in the environment and in some foods so the body does deal with them up to a point. It's higher regular doses that overwhelm the body's ability to remove it that are a problem.

[EDIT] Also note that Boric Acid is often used in eye wash solutions at 1-2% (1750 - 3500 ppm) so should not be irritating to the eye in pools. Also, the video link in the next post may not work anymore so one can use this link instead to learn how borates kill insects but at low concentrations are not a problem for humans. [END-EDIT] [EDIT] The boron content of some foods is listed in this link. Note that the Tolerable Daily Intake (TDI) in these tables is around 0.4 mg/kg/day (which is also quoted here) so is higher than the 0.088 used by the EPA for pool exposure for humans. [END-EDIT] [EDIT] For toxicity, LD50 oral toxicity (where 50% of subjects are killed) is 3450 mg/kg for male rats and >631 mg/kg for beagle dogs. Note that plain table salt has oral toxicity of 3000 mg/kg for rats so is similar to concentrated borate products. [END-EDIT]

[EDIT] Europe does not sell boron products such as borax or boric acid for consumer use in concentrated form as with Borax for laundry or boric acid as an insecticide. The reason is that the European Commission (EC) looked at essentially the same data as the EPA, but have different labeling requirements where the chronic effects data already referred to in the dog and rat studies showed developmental/reproductive issues at the observed effect levels (the EC uses 9.6 mg/kg/day as the NOAEL so no observed adverse effects). This link gives more detail and this link shows the required labeling. Interestingly, some cosmetic products may contain boron chemicals at < 5.5% concentration and are not required to have "Toxic to reproduction, category 1B" labeling. This makes no sense since it basically says that you can use the product on your skin, but you can't use a concentrated product (near 100% boric acid) that when added to pools dilutes to 50 ppm (0.005%) so is 1100 times less concentrated. Yes, there should be handling warnings for concentrated product, but its use is not in concentrated form. Unfortunately, no manufacturer that I am aware of is offering borax or boric acid to consumers because they want to avoid labeling they believe would result in virtually zero sales. [END-EDIT]

Re: Are Borates Safe to Use?

The good news for humans is that since we have kidneys and liquid/water based excretion system we are able to rid ourselves of the boron that hasn't be used in our skeletal stuctures, besides also having a fairly substantial mass and billions more cells.

But, I would guess that injesting pool water, while unavoidable in small quantities, is still not a good idea.

Re: Are Borates Safe to Use?

The video link is no longer active though I found this link that currently works, but I also found this link explaining how boric acid kills insects by starving them. The NAD+ enzyme, shown here, has a cis-diol (two hydroxyl groups attached to adjacent carbons and in the same plane) which reacts with boric acid to form an ester (oxygen) bond, similar to what happens with boric acid and mannitol in some borate test kits. The binding up of most or all of the NAD+ prevents normal digestion from occurring so the insects starve. Insects are unable to efficiently excrete boric acid so it builds up, unlike in mammals that are able to excrete boric acid (up to a point -- beyond which boric acid becomes toxic).

Re: Are Borates Safe to Use?

So there is a lot of scientific data but I'd like to know if anyone in this forum has had any health issues with their dogs after adopting this method? I have a 100 pound lab who loves to swim, but doesn't drink the water from the pool intentionally. I am sure he gets water in his mouth from normal swimming but I have no idea how much he ingests from normal swimming. It seems to me borates are generally harmless from everything I have read but if anyone has any directly related health stories I'd be interested hearing them. I am sure borates can be harmful if I make a borate pie and serve it to my dog. I want to try this so badly but I do not want to put my dog in danger. Thank you.

Re: Are Borates Safe to Use?

There are no reports of health problems with pets due to borates in pool water at all. Even if your pet gets 100% of their drinking water from the pool they will still be (just) below the threshold of detectable symptoms. As long as your pet is getting the great majority of their drinking water somewhere else there is a very reasonable safety margin.

Re: Are Borates Safe to Use?

A 100 pound dog would need to drink 8 liters (over 8 quarts) of 50 ppm borate pool water every day just to be at the No Observed Adverse Effect Limit (NOAEL). The level seen for first symptoms is 3 times higher than this amount. And this is literally drinking every day since borates are excreted from the body and do not accumulate so the daily intake level where problems would occur is that which is higher than the rate at which the body flushes out borates. Boron is an essential nutrient so the body takes in what it needs and excretes the rest, though this process has its limits which is why almost anything is toxic if given in high enough doses. This excretion process is fairly efficient for mammals that use urine primarily to excrete excess nitrogen as urea, but for insects they excrete solid uric acid so do not excrete boron efficiently which is why boron is far more toxic to them.

Re: Are Borates Safe to Use?

Hi everyone, I have an autistic son who loves to swim. Getting him to keep his mouth closed while swimming is an impossibility.... I am concerned about the amount of borate water he would drink, based on JasonLion's math, he could tolerate up to 4 litres a day being 25 kilos.....? Is this correct? Because I don't think he'd swallow that much pool water each day he swims... I hope not anyway...

Re: Are Borates Safe to Use?

The EPA limit has a margin of safety of a factor of 100 which for 25 kilograms would be around 3 tablespoons per day. The somewhat more than 4 liters is without that margin of safety. Remember that this is to get one to the highest level where there were still no symptoms in the studies with dogs and the margin of safety is a factor of 10 since tests were not done on humans and another factor of 10 to account for differences between individuals. So the limit is conservative. This isn't something we'll be able to decide for you. The risk is low, but this is your son. If he were drinking a lot of pool water, then he would probably urinate a lot since drinking a lot of extra water isn't usually retained.